This program rewrites legacy assignment forms to equivalent var or set forms:

a = foo
# becomes:
var a = foo

# but when $a is already defined...
a = foo
# becomes:
set a = foo

If the assignment form contains a mix of existing and new variables, it is rewritten to a var form that declares the non-existing variables and a set form:

a = foo
a b = lorem ipsum
# becomes
var a = foo
var b; set a b = lorem ipsum

The version of the set command in 0.15.x and 0.16.x contained a bug where it could also create variables. This program also rewrites such uses of set by declaring those variables with var first:

set a = foo
set a b = lorem ipsum
# becomes
var a; set a = foo
var b; set a b = lorem ipsum

This program also rewrites legacy lambda syntax to the new syntax, moving arguments and options within [...] before { to within |...| after {.

x = [a b &k=v]{ ... }
# becomes
x = {|a b &k=v| ... }

The new lambda syntax is supported since 0.17.0. If your script still needs to support older versions, you can turn off lambda rewrite with -lambda=false.

This program does not handle any other changes introduced in 0.17.

In the legacy assignment form, the RHS may refer to the just declared variable, such as:

m = [&x={ put $m }]

This will get rewritten to the following, which doesn't work since the var form now evaluates the RHS before declaring the variable:

var m = [&x={ put $m }]

You will need to manually rewrite this to:

var m
set m = [&x={ put $m }]

Build this program:

go install github.com/elves/upgrade-scripts-for-0.17@main

This will install the program to ~/go/bin by default. Add ~/go/bin to your PATH, or copy the program to somewhere already on PATH.

Command line invocation works like gofmt - there are 3 modes:

upgrade-scripts-for-0.17 # no arguments; rewrite stdin to stdout
upgrade-scripts-for-0.17 a.elv b.elv # rewrites script to stdout
upgrade-scripts-for-0.17 -w a.elv b.elv # rewrites script in place

If you're invoking it from Elvish, use the following to rewrite all Elvish scripts in the current directory recursively:

upgrade-scripts-for-0.17 -w **[type:regular].elv

Remember to back up the files, or make sure that they are in version control, just in case this program has bugs and renders your scripts unusable.